Adolescents are at great risk for sexually transmitted diseases (STDs) including HIV/AIDS, and are one of few HIV risk groups for whom HIV/AIDS incidence is not declining (CDC, 2005a). Compared to the general adolescent population, adolescents involved with the criminal justice system are younger at first intercourse, have a greater number of sex partners, and lower rates of condom use, resulting in higher rates of unintended pregnancy and STDs (e.g., Teplin, Mericle, McClelland & Abram, 2003). Data from our previous research efforts suggests that it is heavy alcohol use in concert with sexual activity, rather than heavy alcohol use generally, that is most strongly related to lack of condom use (Bryan, Ray, & Cooper, in press). Further, we have demonstrated initially higher rates of condom use at follow-up among adolescents who participated in a combined sexual risk reduction + alcohol risk reduction intervention as compared to a sexual risk reduction only intervention and an information only control intervention in our prior NIAAA-supported randomized controlled intervention with incarcerated adolescents, (R01 AA013844-01; Schmiege, Broaddus, Bryan, et al., 2008). The goal of the proposed study is to build on those successful findings, and on our ongoing work (RO1 DA019139-01) and that of others (Lebeau-Craven et al., 2003; Kingree & Betz, 2003) which suggests that marijuana use is more prevalent than alcohol use generally and during sex than is alcohol use among criminally-involved adolescents. In addition, NIDA has noted that marijuana is a specific drug of abuse that may be an emerging risk factor for HIV and STDs, but one for which there is little basic or intervention research. In this continuation, we propose to conduct a second randomized controlled trial to compare an expanded sexual risk reduction intervention that includes both an alcohol component and a marijuana component, to a sexual risk reduction intervention that includes only an alcohol component, and a sexual risk reduction only condition. Each of these interventions includes a standard theory-based didactic presentation of sexual reduction intervention material and a group motivational enhancement therapy component focused on alcohol and marijuana, alcohol use only, or sexual risk behavior only. We hope to show that: 1) combining both substances into one intervention further increases its efficacy at decreasing sexual risk behavior because of its broad coverage of the three most highly prevalent risk behaviors (alcohol, marijuana, and unprotected sex) in this population, 2) it is the substance use content, and not the group MET modality that is responsible for this increased efficacy, and 3) the intervention exerts its effects through theoretically-based mediators. The relative success of these interventions will have implications for HIV/STD risk reduction programming for high risk adolescents in the criminal justice system.